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Biomedical subjects

R Samuel

Publications and source records attributed to R Samuel.

At least 37 records · Page 2Linked to original sources
PubMed1993

Anticipatory co-articulation in the speech of young normal and hearing-impaired French Canadians.

The anticipatory co-articulation in the speech of a group of 10 normal young French Canadians (5 boys, 5 girls) was compared to that found in age-matched groups of 10 moderately hearing-impaired and 10 profoundly hearing-impaired French Canadians. The speech stimuli were the syllables /ti/, /tu/, /ki/, and /ku/, elicited five times each in random order. Acoustic evidence (F2 and centroid frequency measures) of co-articulation was found for all groups; however, the degree of co-articulation was smaller and less consistent across consonants for the two hearing-impaired groups. In particular, the moderately hearing-impaired subjects exhibited a reversal of the expected pattern for [ki] and [ku] stimuli; the profoundly hearing-impaired subjects did not produce sufficient [ki] and [ku] stimuli to measure co-articulatory effects reliably. In general, the profoundly hearing-impaired subjects exhibited the smallest acoustic changes as a result of the vocalic influence on the preceding consonant. Results are considered in relation to theories of speech production deficits in hearing-impaired speakers.

Child↗
PubMed1992

Responsiveness to 1,25-dihydroxyvitamin D3 is reduced in lymphocytes from osteoporotic women.

The purpose of this work was to test the hypothesis that reduced responsiveness of target organs to 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] is associated with osteoporosis. Peripheral blood mononuclear (PBM) cells have been previously shown to be a valid model for the action of 1,25(OH)2D3 on its classic target organs in various pathologic and physiologic situations. The responsiveness of lymphocytes to the hormone can be assessed by the extent of inhibition it exerts on the proliferative response to mitogenic lectins. A group of 39 postmenopausal women, at least 10 years after the menopause, participated in the study. Osteoporosis, defined as the presence of at least one nontraumatic vertebral crush fracture, was diagnosed in 19 subjects. Mitogenesis of PBM cells stimulated by phytohemagglutinin and cultured for 72 h in the presence or absence of 1,25-(OH)2D3 (0.03-1 nmol/liter) was assessed by [3H]thymidine incorporation during a 4 h pulse. The maximal inhibitory effect of 1,25-(OH)2D3 at saturating concentration (1 nM/liter) was 74.6 +/- 2.8% (mean +/- SEM) for normal compared to 65.3 +/- 2.9% for osteoporotic women (P = 0.015). The geometric mean of the ED50 values of 1,25-(OH)2D3 was 60% higher in the osteoporotic than in the normal group (P = 0.035). Our data are consistent with the notion that reduced responsiveness of target organs to 1,25-(OH)2D3 is associated with osteoporosis.

Aged↗
PubMed1991

Significance of circumsporozoite-specific antibody in the natural transmission of Plasmodium falciparum, Plasmodium vivax, and Plasmodium malariae in an aboriginal (Orang Asli) population of central peninsula Malaysia.

Two hundred and seventy-five Orang Asli volunteers living in nine villages in the Pos Legap Valley of Perak State, peninsular Malaysia, participated in a prospective study designed to characterize the epidemiological, parasitological, and entomological characteristics of Plasmodium falciparum, P. vivax, and P. malariae malaria transmission. Prevalence rates for the three plasmodial species at initiation of the study ranged from 56% in the 0-4-year-old age group to 0% in individuals over the age of 40. Entomological surveys were conducted, enabling us to determine mosquito salivary gland-positive rates and entomological inoculation rates of 1.2 infectious mosquito bites per person per month for P. falciparum, 2.4 for P. vivax, and 0.3 for P. malariae. Cumulative incidence rates over the 16 weeks of the study, following radical cure of all volunteers, were 22.5% for P. falciparum, 12.7% for P. vivax, and 1.5% for P. malariae. The median baseline antibody titer against the immunodominant repetitive B cell epitope of P. falciparum or P. vivax circumsporozoite protein was significantly higher for volunteers who did not become parasitemic. Volunteers were selected for further study if they had evidence of being challenged with P. falciparum sporozoites during the study, based on a two-fold or greater increase in antibody titer against the immunodominant repetitive B cell epitope of the circumsporozoite protein. Resistance to infection was seen in six of 10 individuals who had high (greater than 25 OD units) baseline ELISA titers, compared with only three of 24 individuals who had low baseline ELISA titers (chi 2 P less than 0.02). A similar analysis for P. vivax did not show a significant correlation.

Adolescent↗
PubMed1988

Tumoral calcinosis revisited--common and uncommon features. Report of ten cases and review.

Familial cutaneous and subcutaneous tumoral calcifications are a recognized entity of unknown pathogenesis. The course of calcinosis and various treatments are discussed and the literature concerning the aetiology is reviewed. Our ten cases provided some experience in dealing with tumoral calcinosis and demonstrated, in addition, some clinical phenomena unrecognized previously, such as involvement of the mucous membranes and an erythematous rash preceding the development of calcified nodules.

Adolescent↗
PubMed1987

"Idiopathic" hypercalciuria and hereditary hypophosphatemic rickets. Two phenotypical expressions of a common genetic defect.

Among 59 closely related members of one Bedouin tribe, we identified 9 who had the characteristic features of hereditary hypophosphatemic rickets with hypercalciuria (HHRH). We found "idiopathic" hypercalciuria in 21 of the 50 asymptomatic members. The biochemical abnormalities observed in these 21 subjects were qualitatively similar to those in the 9 with HHRH, but were quantitatively milder. The urinary calcium concentration was 0.43 +/- 0.14 mg per milligram of creatinine (mean +/- SD) in the patients with HHRH, 0.34 +/- 0.07 in the subjects with idiopathic hypercalciuria, and 0.14 +/- 0.05 in normal subjects from the same tribe. Tubular reabsorption of phosphorus and serum phosphorus concentrations were 3.0 and 4.3 SD units below the age-related mean, respectively, in HHRH, and 1.1 SD units below the normal mean for both variables in idiopathic hypercalciuria. Mean serum levels of 1,25-dihydroxyvitamin D (1,25-(OH)2D) were 303 pg per milliliter in HHRH and 145 pg per milliliter in idiopathic hypercalciuria (upper normal limit, 110). We conclude that the subjects with hypercalciuria and the patients with HHRH shared a hereditary renal phosphate leak that led to hypophosphatemia, elevated serum concentrations of 1,25-(OH)2D, increased intestinal calcium absorption, and hypercalciuria. The magnitude of the hypophosphatemia, which regulates 1,25-(OH)2D levels, appears to determine which subjects will have hypercalciuria alone and which will also have bone disease.

Adolescent↗
PubMed1985

Hereditary hypophosphatemic rickets with hypercalciuria.

We studied a new hereditary syndrome of hypophosphatemic rickets and hypercalciuria in six affected members of one kindred. In all patients, the manifestations of disease began in early childhood. The characteristic features are rickets, short stature, increased renal phosphate clearance (the ratio between the maximal tubular reabsorption rate for phosphorus and the glomerular filtration rate [TmP/GFR] is 2 to 4 S.D. below the age-related mean), hypercalciuria (8.6 mg of urinary calcium per kilogram of body weight per 24 hours vs. the upper normal value of 4.0), normal serum calcium levels, increased gastrointestinal absorption of calcium and phosphorus, an elevated serum concentration of 1,25-dihydroxyvitamin D (390 +/- 99 pg per milliliter vs. the upper normal value of 110), and suppressed parathyroid function (an immunoreactive parathyroid hormone level of 0.33 +/- 0.1 ng per milliliter and a cyclic AMP level of 1.39 +/- 0.12 nmol per deciliter of glomerular filtrate vs. the lower normal values of 0.3 and 1.5, respectively). Long-term phosphate supplementation as the sole therapy resulted in reversal of all clinical and biochemical abnormalities except the decreased TmP/GFR. We propose that the pivotal defect in this syndrome is a renal phosphate leak resulting in hypophosphatemia with an appropriate elevation of 1,25-dihydroxyvitamin D levels, which causes increased calcium absorption, parathyroid suppression, and hypercalciuria. This syndrome may represent one end of a spectrum of hereditary absorptive hypercalciuria. Our observations support the importance of phosphate as a mediator in controlling 1,25-dihydroxyvitamin D production in human beings.

Calcium↗
PubMed1985

Hypercalciuric rickets: metabolic studies and pathophysiological considerations.

Extensive metabolic studies were performed in a 14-year-old boy suffering from the rare clinical entity known as childhood idiopathic hypercalciuria associated with dwarfism, renal tubular abnormalities and bone lesions. The salient features were: hyperphosphaturia with hypophosphatemia, hypercalciuria with normocalcemia, elevated serum 1,25-dihydroxycholecalciferol[1,25(OH)2D3] levels, marked intestinal hyperabsorption of calcium and phosphorus, with low serum parathyroid hormone (PTH) and urinary adenosine 3':5'-cyclic monophosphate (c-AMP). Bone biopsy confirmed the clinical and radiological diagnosis of rickets. It appears that the following pathophysiological sequence is operating: primary renal phosphate leak with hypophosphatemia, increased 1,25(OH)2D3 synthesis, enhanced intestinal calcium absorption which in turn inhibits release of PTH and c-AMP. Hypercalciuria is seen to be secondary to both avid intestinal calcium absorption and depressed PTH activity, and rickets the result of phosphate depletion. Treatment with oral phosphorus only resulted in an acceleration of growth rate, cure of rickets, and return of urinary calcium excretion to normal values.

Adolescent↗
PubMed1984

Glycine pools and turnover rates in leukaemia patients measured with [15N]glycine.

Turnover parameters for plasma glycine were measured by administration of a single dose of [15N]glycine to overnight fasted healthy volunteers, nine patients with chronic leukaemia, one patient with acute monocytic leukaemia and one patient with chronic myeloid leukaemia before and after chemotherapy. Gas chromatography-mass spectrometry was used to determine plasma [15N]glycine enrichment. Pool sizes and turnover rate constants were estimated from time-decay curves for isotope enrichment. Turnover rate constants and metabolic clearance rates of plasma glycine in leukaemia patients were elevated in comparison with data for healthy volunteers. The increased rates of glycine disappearance from the circulation were not accompanied by a depletion in glycine pool size. Turnover rate constants fell during chemotherapy and were within the normal range during remission. There was a significant positive correlation between glycine turnover rate constants and leucocyte counts. The increase in glycine turnover rate constants may be related to proliferation of the neoplastic cells.

Female↗
PubMed1980

End-organ resistance to 1,25-dihydroxycholecalciferol.

A 13-year-old girl with total alopecia who in infancy had rickets unresponsive to large doses of vitamin D2 is described. She had profound hypocalcaemia which was resistant to treatment with high doses of dihydrotachysterol, 1 alpha-hydroxycholecalciferol, and 1,25-dihydroxycholecalciferol. Serum concentrations of 25-hydroxyvitamin D were normal but those of 1,25-dihydroxycholecalciferol were markedly raised (674 and 745 pg/ml). In addition, 24,25-dihydroxyvitamin D was undetectable in serum. Administration of synthetic 24,25-dihydroxycholecalciferol was followed by normocalcaemia which persisted long after treatment was stopped. Her sister, who died at the age of 10 months, also had had total alopecia, rickets, and hypocalcaemia resistant to vitamin-D2 therapy. In this familial syndrome there seems to be end-organ resistance to the action of 1,25-dihydroxycholecalciferol, possibly as a result of changes at the receptor sites.

Adolescent↗
PubMed1976

Secondary pituitary insufficiency: report of three cases of ectopia or hemiagenesis of the thyroid gland.

Three patients with clinical and laboratory manifestations suggestive of pituitary insufficiency due to the presence of a pituitary tumor were found to have long-standing myxedema. The insidious appearance of the signs of hypothyroidism was explained by the cause of their disease--an ectopic thyroid gland in two patients and hemiagenesis of the thyroid in the third. Early recognition and treatment of such cases is important.

Adult↗